Purified polymeric materials and methods of purifying polymeric materials

ABSTRACT

A method is disclosed to purify a polymeric material by filtering a melt comprising poly(arylene ether) and poly(alkenyl aromatic) through a melt filtration system. The method provides a filtered polymeric composition having reduced levels of particulate impurities. The filtered polymeric composition prepared is suitable for use in data storage media applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/648604, filed Aug. 26, 2003, which is hereinincorporated by reference in its entirety.

BACKGROUND OF INVENTION

The present methods are directed to purifying polymeric material byfiltering melts comprising poly(arylene ether) and/or poly(alkenylaromatic) resins. The methods are more particularly directed tofiltering melts comprising poly(arylene ether) and/or poly(alkenylaromatic) resins to result in filtered polymeric materials havingreduced amounts of particulate impurities.

Optical, magnetic and magneto-optic media are primary sources of highperformance storage technology that enable high storage capacity coupledwith a reasonable price per megabyte of storage. Areal density,typically expressed as billions of bits per square inch of disk surfacearea (gigabits per square inch (Gbits/in²)), is equivalent to the lineardensity (bits of information per inch of track) multiplied by the trackdensity in tracks per inch. Improved areal density has been one of thekey factors in the price reduction per megabyte, and further increasesin areal density continue to be demanded by the industry.

In the area of optical storage, advances focus on access time, systemvolume, and competitive costing. Increasing areal density is beingaddressed by focusing on the diffraction limits of optics (usingnear-field optics), investigating three dimensional storage,investigating potential holographic recording methods and othertechniques.

Polymeric data storage media has been employed in areas such as compactdisks (CD) and recordable or re-writable compact discs (e.g., CD-RW),and similar relatively low areal density devices, e.g. less than about 1Gbits/in², which are typically read-through devices requiring theemployment of a good optical quality substrate having low birefringence.

Unlike the CD, storage media having high areal density capabilities,typically up to or greater than about 5 Gbits/in², employ first surfaceor near field read/write techniques in order to increase the arealdensity. For such storage media, although the optical quality of thesubstrate is not relevant, the physical and mechanical properties of thesubstrate become increasingly important. For high areal densityapplications, including first surface applications, the surface qualityof the storage media can affect the accuracy of the reading device, theability to store data, and replication qualities of the substrate.

While there are materials presently available for use in data storagemedia, there remains a need for additional polymeric materialspossessing the combined attributes necessary to satisfy the increasinglyexacting requirements for data storage media applications.

SUMMARY OF INVENTION

In one embodiment, the above-described needs are alleviated by a methodof purifying a polymeric material comprising melt blending poly(aryleneether) and poly(alkenyl aromatic) in an extruder to form a melt (alsocalled a melt mixture); and filtering the melt through a melt filtrationsystem to produce a filtered polymeric material.

In another embodiment, the melt filtration system utilizes a screenpack, a sintered metal filter, or a combination thereof. In anotherembodiment; the melt has an average residence time in the extruder ofless than or equal to about 5 minutes.

In another embodiment, a composition comprising poly(arylene ether) andpoly(alkenyl aromatic) is provided wherein the composition has less than30, preferably less than 20, more preferably less than 10, particulateshaving an average diameter of 30 micrometers per gram of thecomposition.

In another embodiment, a composition comprising poly(arylene ether) andpoly(alkenyl aromatic) is provided wherein the composition has less than200, preferably less than 140, more preferably less than 100,particulates having an average diameter of 20 micrometers per gram ofthe composition.

In another embodiment, a filtered polymeric composition is provided thathas less than 30, preferably less than 20, more preferably less than 10,particulates of 30 micrometer average diameter per gram of the filteredcomposition in combination with less than 200, preferably less than 140,more preferably less than 100, particulates having an average diameterof 20 micrometer per gram of the filtered composition.

In another embodiment, filtered compositions, including theaforementioned filtered compositions, are provided wherein thecompositions contain zero particulates having an average diameter of 175micrometers or larger, preferably 140 micrometers or larger, and morepreferably 100 micrometers or larger, per gram of the filteredcomposition. Other embodiments, including articles made from thefiltered polymeric material, are described below.

DETAILED DESCRIPTION

Due to the surface quality requirements of high areal density storagemedia, it is desirable that current data storage media are prepared frommaterials containing limited quantities of particulate impurities.Visible particulate impurities, such as gels and carbonized polymericmaterial, are undesirable as an aesthetic defect resulting in aconsumer's perception of an inferior quality product. Particles havingsizes larger than about 50 micrometers can act as stress concentratorsin molded articles, thereby reducing the impact strength of thesearticles. Particulate impurities about 1 micrometer in size contributeto an increase in haze which can affect the transmittance of lightthrough or transparency of articles molded from material containing suchimpurities. Most importantly, particulate impurities may affect surfacequality of storage media thereby affecting read accuracy, data storage,and replication.

Visible particulates or “black specks” are dark or colored particulatesgenerally visible to the human eye without magnification and having anaverage diameter of 30 micrometers or greater. Although some people areable to without magnification visually detect particles having anaverage diameter smaller than 30 micrometers and other people can detectonly particles having an average diameter larger than 30 micrometers,the terms “visible particles,” “visible particulates,” and “blackspecks” when used herein without reference to a specified averagediameter means those particulates having an average diameter of 30micrometers or greater. Black specks, as well as other smallermicroscopic particulates, are typically present in poly(arylene ether)compositions as the poly(arylene ether) is subject to oxidativedegradation at high temperatures. Poly(arylene ether)s tend to formcarbonized “black specks” when processed at the high extruder shearrates and/or at high temperatures for extended periods of time as aretypically used in the manufacture of compositions of poly(arylene ether)and poly(alkenyl aromatic) resins.

The above-described needs are alleviated by a method of purifying apolymeric material comprising melt blending poly(arylene ether) andpoly(alkenyl aromatic) in an extruder to form a melt; and filtering themelt through a melt filtration system to produce a filtered polymericmaterial. The melt generally has an average residence time in theextruder of less than or equal to about 5 minutes. The filtrationremoves particulate impurities present in the polymeric material toresult in a filtered polymeric material comprising reduced quantities ofparticulate impurities.

As used herein the term “polymeric material” is inclusive of acomposition comprising poly(arylene ether) resin and poly(alkenylaromatic) resin.

As described herein, melts of polymer mixtures, such as poly(aryleneether) and poly(alkenyl aromatic) mixtures, may be melt filtered toremove particulate impurities. The residence time, temperature, andshear rate of the melt in the extruder should be controlled to minimizedecomposition of the polymeric material, especially the poly(aryleneether) component. Poly(arylene ether)s are known to oxidize and formgels if maintained at high temperatures. These resins may also formcarbonized “black specks” or degrade in color (darken) if processed athigh temperatures for extended periods of time. Therefore, it ispreferable to minimize the residence time of the melt by selection ofextruder length and extruder screw design and by controlling the screwspeed and feed rate. An average residence time of less than or equal toabout 5 minutes may be employed, with less than or equal to about 2minutes preferred, and less than or equal to about 1 minute morepreferred.

It is also preferable to minimize the residence time of the melt throughthe melt filtration system. The melt filtration system may be designedto provide short residence times based on, among other options, theselection of the surface area of the filter, the type of filter, andvolume of the melt filtration housing. A higher filter surface area anda smaller housing volume can provide shorter residence times.

The melt filtration system of the extruder is preferably located at theterminal barrel of the extruder, and more preferably at the die head ofthe extruder. The extruder may comprise a single melt filtration systemor multiple melt filtration systems, including combinations of differenttypes of melt filtration systems.

Any type of extruder that is capable of providing a homogenous melt ofpoly(arylene ether), poly(alkenyl aromatic) and/or additional resins andadditives, may be used. Useful types of extruders include, for example,a twin screw counter-rotating extruder, a twin screw co-rotatingextruder, a single screw extruder, a single screw reciprocatingextruder, a kneader, a ring extruder, a combination of the foregoing,and the like. Preferably a single extruder may be used, but multipleextruders may be employed.

Although single screw extruders may be utilized, it is generallypreferable to use multi-screw extruders due to their greater pumpingcapability through the melt filtration system. Twin-screwcounter-rotating extruders, such as those manufactured by LeistritzExtrusionstechnik and NFM Welding-Engineers, are useful and are oftenpreferred where higher pressures or longer residence times are desired.Conical counter-rotating twin-screw extruders, such as thosemanufactured by Milacron, are also preferred due to large feedcapabilities and high pumping efficiencies. Twin-screw co-rotating,intermeshing extruders, such as those manufactured by CoperionWerner-Pfleiderer, are especially preferred due to their highthrough-put rates, short residence times, flexible screw designs,outstanding alloying, and other design benefits. Both three-lobe andtwo-lobe machines are generally useful with two-lobe machines generallypreferred due to their higher throughput rates. Ring extruders, such asthose manufactured by 3+ Extruder GmbH, are also useful and typicallycomprise a ring of three to twelve small screws or grooved rolls arounda static rod or core. The screws co rotate and intermesh on two sidesproviding good dispersive and distributive mixing as well as the abilityto control the residence time of the material in the extruder. Theintermeshing design also provides two clean wipes to the screw's shear,mixing, and kneading elements.

The extruder length should be sufficient to allow for melting andintimate admixing of the polymeric components and any additionaladditives as well as optionally venting of the melt mixture. Extrudersas short as five barrel sections may be employed, although longerextruders are also useful.

When preparing blends of poly(arylene ether) solvent, monomers, andother low molecular weight materials are removed from the extruderthrough the vent system. A particularly useful process to improve theremoval of volatile substances from poly(arylene ether) or poly(aryleneether) resin blends includes steam stripping as describe in U.S. Pat.No. 5,204,410 to Banevicius et al., U.S. Pat. No. 5,102,591 to Hasson etal., U.S. Pat. No. 4,994,217 to Banevicius, and U.S. Pat. No.4,992,222to Banevicius et al. Steam stripping is typically performed in anextruder comprising ports for the injection of water or steam andsufficient vacuum vent capability to remove the stripped volatiles andwater. Water or steam are the preferred stripping agents, and theproportion employed is up to about 15 percent by weight of the polymercomposition, to be divided equally, or unequally, among the two or moreinjection ports located along the length of the extruder barrel. Thepreferred proportion is from about 0.25 to about 15 weight percent,since an amount within this range is generally very effective forremoval of volatiles without burdening the vacuum system. Most preferredis from 0.5 to about 5 weight percent.

Blanketing of the internal free space of the extruder with an inert gasto minimize the exposure of molten polymer to oxygen is also useful tominimize gel and black speck formation. By inert is meant a gas thatdoes not result in oxidation or other chemical reaction with the moltenpolymeric composition as is generally substantially oxygen-free.Generally, nitrogen is used due to its low cost and ready availability,although other inert gases are also contemplated. Nitrogen (or otherinert gas) can be added into one or more of the feeder systems, extruderfeed zones, vents, melt filtration systems, and other areas of theextruder in which the molten polymer can come into contact with oxygen.

Also contemplated are extruders comprising one or more side feedersalong the extruder barrel suitable to feed additional components to themelt. Additional components include additional resins, functionalizingagents and/or additives.

The extruder is preferably run at temperatures suitable to produce anintimate blend of the components that compose the melt mixture, but lowenough to minimize decomposition of the melt mixture. A range ofextruder temperatures that may be employed are of about 260° C. to about380° C. Within this range a temperature of less than or equal to about340° C. may be employed, and less than or equal to about 320° C. morepreferred. Also within this range a temperature of greater than or equalto about 280° C. may be employed, and greater than or equal to about290° C. preferred. Within the range of extruder temperatures, the meltmixture generally has a temperature between about 280° C. and about 340°C.

The conditions selected to begin and end the melt blending and meltfiltering operations are important to control so as to minimize theformation of gels and black specks during the process. When an extruderis utilized, residual material remains that is subjected to extendedperiods at high temperatures and can lead to formation of gels and blackspecks. In the practice of the present invention, it is preferred tobegin the process with equipment that has been disassembled and cleanedof residual material so as to start with an empty equipment set althoughin commercial operations, such disassembly is often not feasible.Generally, a material that is compatible with the resin composition thathas good thermal and oxidation stability, e.g., polystyrene, will beused to start the machine. Upon reaching a steady operating state, thecomposition is adjusted to achieve the desired formulation. It istypical to have an elevated number of gels and black specks during thestart-up operation followed by a reduction to a steady state as may bedetermined via an on-line or off-line quality monitoring system.

When a twin-screw extruder is employed, the extruder operation may bedefined by a specific throughput rate of about 0.5 kg/hr/cm³ to about8.0 kg/hr/cm³. The specific throughput rate is defined as the throughputrate of the melt divided by the diameter³ of the extruder barrel. Withinthis range a specific throughput rate of less than or equal to about 7.5kg/hr/cm³ may be employed, and less than or equal to about 7 kg/hr/cm³preferred. Also within this range a throughput rate of greater than orequal to about 3 kg/hr/cm³ may be employed, and greater than or equal toabout 5 kg/hr/cm³ preferred.

In one embodiment, a melt pump or gear pump is used in combination withthe extruder to provide sufficient rate and pressure of a flow of meltthrough the melt filtration system. The melt pump also provides thecapability to control and maintain an even flow of melt through theextruder system resulting in a more uniform polymeric material.

In one embodiment, the poly(arylene ether), poly(alkylene aromatic), andoptional additional components may be mixed together prior to the meltblending step. Any known equipment capable of intimately admixing thecomponents may be used, for example, mixers capable of applying shear tothe components, conical screw mixers, V-blenders, twin screwcompounders, Henschel mixers, ribbon blenders, and the like.

Any suitable melt filtration system or device that can removeparticulate impurities from a melt mixture comprising poly(aryleneether), poly(alkenyl aromatic), or a combination of the two, may beused. Preferably, the melt is filtered through a single melt filtrationsystem, although multiple melt filtration systems are contemplated.

Suitable melt filtration systems include filters made from a variety ofmaterials such as, but not limited to, sintered-metal, metal mesh orscreen, fiber metal felt, ceramic, or a combination of the foregoingmaterials, and the like. Particularly useful filters are sintered metalfilters exhibiting high tortuosity, including the sintered wire meshfilters prepared by Pall Corporation and Martin Kurz & Company, Inc.

Any geometry of melt filter may be used including, but not limited to,cone, pleated, candle, stack, flat, wraparound, screens, cartridge, packdisc, as well as a combination of the foregoing, and the like. Theselection of the geometry can vary depending on various parameters suchas, for example, the size of the extruder and the throughput ratedesired as well as the degree of particle filtration that is desired.Preferred materials of construction include stainless steels, titanium,nickel, as well as other metals alloys. Various weaves of wire fabricincluding plain, dutch, square, and twill can be used. Especially usefulare filters that have been designed to minimize internal volume and lowflow areas and to withstand repeated cleaning cycles.

The melt filtration system may include a periodic or continuous screenchanging filter or batch filters. For example, continuous screenchanging filters may include a ribbon of screen filter that is slowlypassed into the path of a melt flow in an extruder. The melt mixturepasses through the filter and the filter collects particulate impuritieswithin the melt and these impurities are carried out of the extruderwith the filter ribbon as it is periodically or continuously renewedwith a new section of ribbon.

The pore size of the melt filter may be of any size ranging from about0.5 micrometer to about 200 micrometers. Within this range, a pore sizeof less than or equal to about 100 micrometers can be employed, withless than or equal to about 50 micrometers preferred, and less than orequal to about 20 micrometers more preferred. Also within this range apore size of greater than or equal to about 1 micrometer may be used,with greater than or equal to about 7 micrometers preferred, and greaterthan or equal to about 15 micrometers more preferred.

The temperature of the melt filtration system is sufficient to maintainthe material in a molten state and at a sufficiently low viscosity forthe material to pass through the filter without excessive pressure drop.Generally useful temperatures range from about 260° C. to about 380° C.Within this range a temperature of less than or equal to about 340° C.may be employed, and less than or equal to about 320° C. more preferred.Also within this range a temperature of greater than or equal to about280° C. may be employed, and greater than or equal to about 290° C.preferred.

In order to operate the overall melt filtering process in a continuousfashion for long periods of time, it is often desirable to employ aby-pass system for the melt filtration system or device. In a by-passsystem, a continuous melt flow is maintained and redirected into areserve melt filtration system or device. The by-pass system can beoperated by a series of automated valves that have been set to engage ata pre-determined value, e.g., predetermined pressure drop or after apredetermined amount of material has been filtered, or can beinterconnected with an in-line or off-line quality monitoring system, ormay be operated or engaged manually. In a preferred embodiment, theprocess is operated under conditions wherein less than a five-fold, morepreferably less that a three-fold, pressure drop is observed as comparedto the initial pressure drop obtained with a clean filtration system.Operation of the melt filtering process in a continuous fashion for longperiods of time generally helps to minimize formation of gels and blackspecks formed during the start-up and shut-down operations and enables amore steady state process to be achieved. Processed materials obtainedduring the start-up and shut-down operations that are outside thedesired particulate level may be reprocessed to avoid wasted material.

The filtered polymeric material obtained is preferably substantiallyfree of visible particulates. “Substantially free of visible particulateimpurities” means that a ten gram sample of polymeric material dissolvedin fifty milliliters of chloroform (CHCl₃) exhibits fewer than fivevisible specks when viewed with the aid of a light box. As previouslyexplained, particles visible to the naked eye are typically thosegreater than 30 micrometers in diameter.

In a preferred embodiment, the filtered polymeric material recoveredfrom the extruder is substantially free of particulate impuritiesgreater than about 20 micrometers, more preferably greater than about 10micrometers. “Substantially free of particulate impurities greater thanabout 20 (or 10) micrometers” means that of a forty gram sample ofpolymeric material dissolved in 400 milliliters of CHCl₃, the number ofparticulates per gram having an average diameter of about 20 (or 10)micrometers is less than 200, as measured by a Pacific Instruments ABS2analyzer based on the average of five samples of twenty milliliterquantities of the dissolved polymeric material that is allowed to flowthrough the analyzer at a flow rate of one milliliter per minute (plusor minus five percent).

In another embodiment, the filtered polymeric material has less than 10black specks, preferably less than 5 black specks, and more preferablyless than 2 black specks, larger than 100 micrometers in averagediameter size per 15 grams of filtered polymeric material. In anotherembodiment, the filtered polymeric material has less than 5 blackspecks, preferably less than 2 black specks, and more preferably noblack specks, larger than 140 micrometers in average diameter size per15 grams of filtered polymeric material. In another embodiment, thefiltered polymeric material has less than 100 black specks, preferablyless than 75 black specks, and more preferably less than 50 blackspecks, within the 20 to 100 micrometer average diameter range per 15grams of filtered polymeric material.

Upon extrusion, the filtered polymeric material may be pelletized bymethods known in the art. For example, strands of filtered polymericmaterial extruded from an extruder or similar device, may be cooled inclean water baths or cooled by water spray and then chopped intopellets. The water, prior to its use in the bath or spray, may befiltered to remove impurities. Likewise the water may be recycled andfiltered during the recycle loop. The water is typically filtered toremove particles greater than about 20 micrometers. De-ionized filteredwater is also generally preferred to remove ionic impurities that mayadhere to the filtered material. When a water bath or spray is employedto regulate the temperature of the extrudate prior to cutting, theextrudate temperature is preferably adjusted to minimize the formationof dust and to help provide a relatively uniform pellet size. When awater bath and/or water spray is utilized, an air knife is typicallyemployed prior to cutting the extrudate. It is preferred to use filteredair in the air knife to avoid contaminating the hot strands withmicrometer-sized particles. A preferred strand temperature is less thanabout 130° C., with less than about 90° C. often more preferred.

Typically, pellets are approximately 2–3 mm in size although smaller orlarger pellets may also be desired. Although a variety of devices may beemployed to cut the extrudate into the desired pellet size, cuttingdevices having multiple rotating blades and metal rollers, for example,stainless steel rollers, are often preferred. Use of rubber rollers canlead to contamination of the filtered polymeric material. Pelletscreeners are often preferably employed to remove undesired pellets thatare too small or too large. When screeners and other devices, such astransfer systems, are employed for handling the pellets, equipmenthaving elastomer components that may lead to pellet contamination aregenerally avoided. The pellets may be dried using techniques standard inthe art including centrifugal dryers, batch or continuous oven dryers,fluid beds, and the like. Optionally, the filtered polymeric materialmay be transferred and isolated as pellets in a “clean room” using, forexample, HEPA air filtration to prevent contamination from thesurroundings. Collection and handling of the filtered resin material ina Class 100 environment is typically preferred. The pellets may bepackaged in a variety of containers provided that such containers do notlead to contamination of the filtered polymeric material. In a preferredembodiment, the pellets are vacuum packaged to draw the containertightly around the contents to reduce the shifting and breakage of thepellets into finer particles during handling and transport.Additionally, vacuum packaging enables an oxygen-free andcontaminant-free environment to be maintained.

One preferred pelletization method employs an underwater die-facepelletizer system. Another preferred pelletization method employs awater ring pelletizer system. A suitable method of pelletizing isgenerally described in U.S. Pat. No. 6,372,175. Useful pelletizingmachines, including die-face pelletizers, are generally described inU.S. Pat. Nos. 3,973,890, 4,421,470, and 5,607,700.

Rather than extruding pellets, the filtered polymeric material may beextruded as fibers, tubes, films, or sheets by appropriate choice of thedie assembly.

Various in-line and off-line monitors may also be employed to judge thequality of the filtered material during the filtering process. Suchmonitors often employ light or laser sensing devices to detect visiblespecks in the extrudate and/or in the pellets. The monitors can beinterconnected with the operation of the processing equipment andprogrammed to automatically adjust the process based upon predeterminedcriteria. Likewise, the monitors may sound alarms to alert the operatorsbased on the predetermined criteria.

The term poly(arylene ether) includes polyphenylene ether (PPE) andpoly(arylene ether) copolymers; graft copolymers; poly(arylene ether)ether ionomers; and block copolymers of alkenyl aromatic compounds,vinyl aromatic compounds, and poly(arylene ether), and the like; andcombinations comprising at least one of the foregoing; and the like.Poly(arylene ether)s per se, are known polymers comprising a pluralityof structural units of the formula (I):

wherein for each structural unit, each Q¹ is independently halogen,primary or secondary lower alkyl (e.g., alkyl containing up to 7 carbonatoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, orhalohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms, or the like; and each Q² is independentlyhydrogen, halogen, primary or secondary lower alkyl, phenyl, haloalkyl,hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atomsseparate the halogen and oxygen atoms, or the like. It will beunderstood that the term “haloalkyl” includes alkyl groups substitutedwith one or more halogen atoms, including partially and fullyhalogenated alkyl groups. Preferably, each Q¹ is alkyl or phenyl,especially C₁₋₄ alkyl, and each Q² is hydrogen or C₁₋₄ alkyl.

Both homopolymer and copolymer poly(arylene ether) are included. Thepreferred homopolymers are those containing 2,6-dimethylphenylene etherunits. Suitable copolymers include random copolymers containing, forexample, such units in combination with 2,3,6-trimethyl-1,4-phenyleneether units or copolymers derived from copolymerization of2,6-dimethylphenol with 2,3,6-trimethylphenol. Also included arepoly(arylene ether) containing moieties prepared by grafting vinylmonomers or polymers such as polystyrenes, as well as coupledpoly(arylene ether) in which coupling agents such as low molecularweight polycarbonates, quinones, heterocycles and formals undergoreaction in known manner with the hydroxy groups of two poly(aryleneether) chains to produce a higher molecular weight polymer. Poly(aryleneether)s used herein may further include combinations comprising at leastone of the above. Preferred poly(arylene ether)s arepoly(2,6-dimethylphenylene ether) and poly(2,6-dimethylphenyleneether-co-2,3,6-trimethylphenylene ether) such as those described in U.S.Pat. No. 6,407,200 to Singh et al. and U.S. Pat. No. 6,437,084 to Birsaket al.

The poly(arylene ether) generally has a number average molecular weightof about 3,000–40,000 atomic mass units (amu) and a weight averagemolecular weight of about 20,000–80,000 amu, as determined by gelpermeation chromatography. The poly(arylene ether) may have an intrinsicviscosity (IV) of about 0.10 to about 0.60 deciliters per gram (dl/g),as measured in chloroform at 25° C. Within this range an IV of less thanor equal to about 0.48 preferred, and less than or equal to about 0.40more preferred. Also preferred within this range is an IV of greaterthan or equal to about 0.29, with greater than or equal to about 0.33dl/g more preferred. It is also possible to utilize a high intrinsicviscosity poly(arylene ether) and a low intrinsic viscosity poly(aryleneether) in combination. Determining an exact ratio, when two intrinsicviscosities are used, will depend somewhat on the exact intrinsicviscosities of the poly(arylene ether) used and the ultimate physicalproperties that are desired.

Suitable poly(arylene ether)s include, but are not limited to,poly(2,6-dimethyl-1,4-phenylene ether);poly(2,3,6-trimethyl-1,4-phenylene) ether; poly(2,6-dimethylphenyleneether-co-2,3,6-trimethylphenylene ether);poly(2,6-diethyl-1,4-phenylene) ether;poly(2-methyl-6-propyl-1,4-phenylene) ether;poly(2,6-dipropyl-1,4-phenylene) ether;poly(2-ethyl-6-propyl-1,4-phenylene)ether;poly(2,6-dilauryl-1,4-phenylene) ether; poly(2,6-diphenyl-1,4-phenylene)ether; poly(2,6-dimethoxy-1,4 phenylene) ether;poly(2,6-diethoxy-1,4-phenylene) ether;poly(2-methoxy-6-ethoxy-1,4-phenylene) ether;poly(2-ethyl-6-stearyloxy-1,4-phenylene) ether;poly(2,6-dichloro-1,4-phenylene) ether;poly(2-methyl-6-phenyl-1,4-phenylene) ether;poly(2-ethoxy-1,4-phenylene) ether; poly(2-chloro-1,4-phenylene) ether;poly(2,6-dibromo-1,4-phenylene) ether;poly(3-bromo-2,6-dimethyl-1,4-phenylene) ether; or a mixture of theforegoing poly(arylene ether)s.

Suitable base titratable functionalized poly(arylene ether) resinsinclude, but are not limited to, those prepared via reaction with anappropriate acid or anhydride functionalization agent. For example thoseprepared by melt reaction of poly(arylene ether) with alpha, betaunsaturated carbonyl compounds, including maleic anhydride, maleic acid,fumaric acid, citraconic anhydride, citraconic acid, itaconic anhydride,itaconic acid, aconitic anhydride, aconitic acid, and their esters andamines; alpha-hydroxy carbonyl compounds including carboxylic acids suchas citric acid and maleic acid; derivatives of5-hydroxybenzene-1,2,4-tricarboxylic anhydride, such as the5-acetyl-derivative or a 4-ester-derivative such as the phenyl ester;trimellitic anhydride aryl esters, including trimellitic anhydridephenyl salicylate; and reaction products and combinations comprising atleast one of the foregoing, among others, can be employed.Alternatively, poly(arylene ether) may be functionalized with acidic orlatent acidic groups in a suitable solvent. Examples of such processesinclude metallation of poly(arylene ether) in tetrahydrofuran (THF)followed by quenching with carbon dioxide or capping of poly(aryleneether) in toluene solution with trimellitic anhydride acid chloride.Typically, less than or equal to about 10 wt % functionalization agentcan be used (based on the weight of the poly phenylene ether and theagent), with less than or equal to about 6 wt % preferred, and about 1.5wt % to about 4 wt % especially preferred.

In one embodiment, the poly(arylene ether) comprises a cappedpoly(arylene ether). The capping may be used to reduce the oxidation ofterminal hydroxy groups on the poly(arylene ether) chain. The terminalhydroxy groups may be inactivated by capping with an inactivatingcapping agent via an acylation reaction, for example. The capping agentchosen is desirably one that results in a less reactive poly(aryleneether) thereby reducing or preventing crosslinking of the polymer chainsand the formation of gels or black specks during processing at elevatedtemperatures. Suitable capping agents include, for example, esters ofsalicylic acid, anthranilic acid, or a substituted derivative thereof,and the like; esters of salicylic acid, and especially salicyliccarbonate and linear polysalicylates, are preferred. As used herein, theterm “ester of salicylic acid” includes compounds in which the carboxygroup, the hydroxy group, or both have been esterified. Suitablesalicylates include, for example, aryl salicylates such as phenylsalicylate, acetylsalicylic acid, salicylic carbonate, andpolysalicylates, including both linear polysalicylates and cycliccompounds such as disalicylide and trisalicylide. The preferred cappingagents are salicylic carbonate and the polysalicylates, especiallylinear polysalicylates. When capped, the poly(arylene ether) may becapped to any desirable extent up to 80 percent, more preferably up toabout 90 percent, and even more preferably up to 100 percent of thehydroxy groups are capped. Suitable capped poly(arylene ether) and theirpreparation are described in U.S. Pat. No. 4,760,118 to White et al. andU.S. Pat. No. 6,306,978 to Braat et al.

Capping poly(arylene ether) with polysalicylate is also believed toreduce the amount of aminoalkyl terminated groups present in thepoly(arylene ether) chain. The aminoalkyl groups are the result ofoxidative coupling reactions that employ amines in the process toproduce the poly(arylene ether). The aminoalkyl group, ortho to theterminal hydroxy group of the poly(arylene ether), is susceptible todecomposition at high temperatures. The decomposition is believed toresult in the regeneration of primary or secondary amine and theproduction of a quinone methide end group, which may in turn generate a2,6-dialkyl-1-hydroxyphenyl end group. Capping of poly(arylene ether)containing aminoalkyl groups with polysalicylate is believed to removesuch amino groups to result in a capped terminal hydroxy group of thepolymer chain and the formation of 2-hydroxy-N,N-alkylbenzamine(salicylamide). The removal of the amino group and the capping providesa poly(arylene ether) that is more stable to high temperatures, therebyresulting in fewer degradative products, such as gels or black specks,during processing of the poly(arylene ether).

Based upon the foregoing, it will be apparent to those skilled in theart that the contemplated poly(arylene ether) resin may include many ofthose poly(arylene ether) resins presently known, irrespective ofvariations in structural units or ancillary chemical features.

The poly(arylene ether)s are typically prepared by the oxidativecoupling of at least one monohydroxyaromatic compound in the presence ofa catalyst system and solvent. There is no particular limitation on themonohydric phenol used in the poly (arylene ether) synthesis. Suitablemonohydroxyaromatic compounds include those according to the followingformula (II)

wherein each Q¹ is independently halogen, primary or secondary loweralkyl (e.g., alkyl containing up to 7 carbon atoms), phenyl, haloalkyl,aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least twocarbon atoms separate the halogen and oxygen atoms, or the like; andeach Q² is independently hydrogen, halogen, primary or secondary loweralkyl, phenyl, haloalkyl, hydrocarbonoxy, or halohydrocarbonoxy whereinat least two carbon atoms separate the halogen and oxygen atoms, or thelike. Preferably, each Q¹ is alkyl or phenyl, especially C₁₋₄ alkyl, andeach Q² is hydrogen or C₁₋₄ alkyl. Preferred monohydroxyphenols include2,6-dimethylphenol and 2,3,6-trimethylphenol.

In one embodiment, the monohydroxyphenol is 2,6-dimethylphenol having apurity of greater than about 99 weight percent, preferably greater than99.67 weight percent, and more preferably greater than 99.83 weightpercent. The 2,6-dimethylphenol preferably comprises less than about0.004 weight percent phenol and more preferably less than 0.003 weightpercent phenol. It is preferred that the 2,6-dimethylphenol contain lessthan about 0.12 weight percent cresol and more preferably less than0.087 weight percent cresol. Cresol includes, for example, o-cresol,m-cresol, p-cresol, or a combination comprising at least one of theforegoing cresols. In a preferred embodiment, the 2,6-dimethylphenolcontains less than about 0.107 weight percent other mono-, di- and/ortrialkylphenols and preferably less than 0.084 weight percent. The othermono-, di- and/or trialkylphenols may include, for example,2,3,6-trimethylphenol, 2,6-ethylmethylphenol, 2-ethylphenol,2,4,6-trimethylphenol, or a combination comprising at least one of theforegoing other mono-, di- and/or trialkylphenols. In another preferredembodiment, the 2,6-dimethylphenol preferably comprises less than about0.072 weight percent of another dimethylphenol besides2,6-dimethylphenol, more preferably less than about 0.055 weight percentof another dimethylphenol. The other dimethylphenol may be2,4-dimethylphenol, 2,3-dimethylphenol, 2,5-dimethylphenol,3,5-dimethylphenol, 3,4-dimethylphenol, or a combination comprising atleast one of the foregoing dimethylphenols. It is believed thatminimizing the amounts of phenol, cresol, other dimethylphenols, andmono-, di-, and/or trialkylphenols in the 2,6-dimethylphenol monomerleads to a reduction in undesired branching or chain stopping reactionsand helps maintain the integrity of the resulting poly(phenylene ether)physical properties.

The oxidative coupling of the monohydric phenol uses anoxygen-containing gas, which is typically oxygen (O₂) or air, withoxygen being preferred.

Suitable organic solvents for the oxidative coupling include aliphaticalcohols, ketones, aliphatic and aromatic hydrocarbons,chlorohydrocarbons, nitrohydrocarbons, ethers, esters, amides, mixedether-esters, sulfoxides, and the like, and combinations comprising atleast one of the foregoing organic solvents, providing they do notinterfere with or enter into the oxidation reaction. Preferred solventsinclude C₆–C₁₈ aromatic hydrocarbons such as benzene, toluene, andxylene; halogenated hydrocarbons such as dichloromethane, andchloroform; and halogenated aromatic hydrocarbons such as chlorobenzeneand dichlorobenzene.

The solvent may comprise, in addition to a C₆–C₁₈ aromatic hydrocarbon,a C₃–C₈ aliphatic alcohol that is a poor solvent for the poly(aryleneether), such as, for example, n-propanol, isopropanol, n- butanol,t-butanol, n-pentanol, and the like, and combinations comprising atleast one of the foregoing C₃–C₈ aliphatic alcohols. The solvent mayfurther comprise, in addition to a C₆–C₁₈ aromatic hydrocarbon and aC₃–C₈ aliphatic alcohol, methanol or ethanol, which act as ananti-solvent for the poly(arylene ether). The C₆–C₁₈ aromatichydrocarbon, the C₃–C₈ aliphatic alcohol, and the methanol or ethanolmay be combined in any proportion, but in some embodiments, it ispreferred that the solvent comprise at least about 50 weight percent ofthe C₆–C₁₈ aromatic hydrocarbon.

Useful catalyst systems typically contain at least one heavy metalcompound such as a copper, manganese or cobalt compound, usually incombination with various other materials. Suitable catalyst systemsinclude cuprous chloride, cupric chloride, cuprous bromide, cupricbromide, cuprous sulfate, cupric sulfate, cuprous tetraamine sulfate,cupric tetraamine sulfate, cuprous acetate, cupric acetate, cuprouspropionate, cupric butyrate, cupric laurate, cuprous palmitate andcuprous benzoate; and similar manganese salts and cobalt salts. Insteadof direct addition of the above-exemplified metal salt, it is alsopossible to add a metal or a metal oxide and an inorganic acid, organicacid or an aqueous solution of such an acid and form the correspondingmetal salt or hydrate.

The catalyst systems may also be complexed with a mono- or dialkylamine,aromatic amines or N,N′-dialkylalkylenediamines. Non-limiting examplesof suitable primary, secondary or tertiary amines include mono- anddimethylamine, mono- and diethylamine, mono- and dipropylamine, mono-and dibutylamine, mono- and dibenzylamine, mono- and dicyclohexylamine,mono- and diethanolamine, methylethylamine, methylpropylamine,methylcyclohexylamine, ethylisopropylamine, benzylmethylamine,octylchlorobenzylamine, methylphenethylamine, benzylethylamine,dimethylbutylamine, N,N′-dialkylethylenediamines such asN,N′-di-tert-butylethylenediamine, and N,N′-di-isopropylethylenediamine,N,N,N′-trialkylethylenediamines, N,N′-dialkylpropylenediamines andN,N,N′-trialkylpropylenediamines.

Known processes to prepare poly(phenylene ether)s include Europeanpatent documents EP 1167421A2; EP1167419A2; and EP1167420A1, all ofwhich are incorporated herein by reference. Further methods forpreparing poly(phenylene ether)s are described, for example, in U.S.Pat. Nos. 6,407,200, 5,250,486; 5,017,655; 4,092,294; 4,083,828;4,054,553; 3,962,181; 3,838,102; 3,733,299; 3,661,848; 3,642,699;3,639,656; 3,365,422; 3,306,875; and 3,306,874. Based upon theforegoing, it will be apparent to those skilled in the art that thecontemplated poly(arylene ether) may prepared by all methods presentlyknown, irrespective of variations in processing conditions, reagents, orcatalysts.

In one embodiment, the poly(arylene ether) is isolated by precipitationand preferably has a copper content of less than about 15 parts permillion and more preferably less than 5 parts per million. Additionally,the precipitated poly(phenylene ether) comprises an amount of titratableamine content of less than about 1.27 weight percent and preferably lessthan 1.18 weight percent. A titratable amine content that is too highresults in a poly(phenylene ether) having a strong odor, while toolittle amine content may result in a polymer having poor mechanicalproperties. In another embodiment, the poly(arylene ether) reactionmixture is filtered to remove, at least in part, gels and otherparticulates prior to isolation of the poly(arylene ether).

The term poly(alkenyl aromatic) resin as used herein includes polymersprepared by methods known in the art including bulk, suspension, andemulsion polymerization, which contain at least 25% by weight ofstructural units derived from an alkenyl aromatic monomer having thestructure (III)

wherein R¹ is hydrogen, C₁–C₈ alkyl, or halogen; Z¹ is vinyl, halogen orC₁–C₈ alkyl; and p is 0 to 5. Preferred alkenyl aromatic monomersinclude styrene, chlorostyrene, and vinyltoluene. The poly(alkenylaromatic) resins include homopolymers of an alkenyl aromatic monomer;random copolymers of an alkenyl aromatic monomer, such as styrene, withone or more different monomers such as acrylonitrile, butadiene,alpha-methylstyrene, ethylvinylbenzene, divinylbenzene and maleicanhydride; and rubber-modified poly(alkenyl aromatic) resins comprisingblends and/or grafts of a rubber modifier and a homopolymer of analkenyl aromatic monomer (as described above), wherein the rubbermodifier may be a polymerization product of at least one C₄–C₁₀nonaromatic diene monomer, such as butadiene or isoprene, and whereinthe rubber-modified poly(alkenyl aromatic) resin comprises about 98 toabout 70 weight percent of the homopolymer of an alkenyl aromaticmonomer and about 2 to about 30 weight percent of the rubber modifier,preferably about 88 to about 94 weight percent of the homopolymer of analkenyl aromatic monomer and about 6 to about 12 weight percent of therubber modifier. These rubber modified polystyrenes include high impactpolystyrene (commonly referred to as HIPS).

The poly(alkenyl aromatic) resins also include non-elastomeric blockcopolymers, for example diblock, triblock, and multiblock copolymers ofstyrene and one or more polyolefins. Non-elastomeric block copolymercompositions of styrene and butadiene can also be used that have linearblock, radial block, or tapered block copolymer architectures whereinthe butadiene component is present up to about 35 weight percent. Theyare commercially available from such companies as Atofina as under thetrademark FINACLEAR and Chevron Phillips Chemical Company under thetrademark K-RESINS.

The poly(alkenyl aromatic) resins may also include block copolymers ofstyrene-polyolefin-methyl methacrylate, especiallypoly(styrene-beta-1,4-butadiene-beta-methyl methacrylate (SBM) availablefrom Atofina comprising blocks of polystyrene, 1,4-polybutadiene, andsyndiotactic polymethyl methacrylate. SBM block copolymers availablefrom Atofina include AF-X223, AF-X333, AF-X012, AF-X342, AF-X004, andAF-X250.

A preferred poly(alkenyl aromatic) is a homopolymer of the alkenylaromatic monomer (III) wherein R¹ is hydrogen, lower alkyl or halogen;Z¹ is vinyl, halogen or lower alkyl; and p is from 0 to 5. Aparticularly preferred homopolymer of an alkenyl aromatic monomer is thehomopolymer derived from styrene (i.e., homopolystyrene). Thehomopolystyrene preferably comprises at least 99% of its weight, morepreferably 100% of its weight, from styrene.

The stereoregularity of the poly(alkenyl aromatic) resin may be atacticor syndiotactic. Highly preferred poly(alkenyl aromatic) resins includeatactic and syndiotactic homopolystyrenes. Suitable atactichomopolystyrenes are commercially available as, for example, EB3300 fromChevron, and P1800 from BASF. Atactic homopolystyrenes are sometimesreferred to herein as “crystal polystyrene” resins. Useful syndiotacticpolystyrene resins (SPS) are available from The Dow Chemical Companyunder the QUESTRA trademark.

The poly(alkenyl aromatic) may have a number average molecular weight ofabout 20,000–100,000 atomic mass units (amu) and a weight averagemolecular weight of about 10,000–300,000 amu.

The filtered polymeric material obtained may comprise poly(aryleneether) in an amount of about 90 to about 10 weight percent andpoly(alkenyl aromatic) in an amount of about 10 to about 90 weightpercent, based on the total weight of the poly(alkenyl aromatic) andpoly(arylene ether) resins. Within this range the amount of poly(aryleneether) may be less than or equal to about 80 weight percent, less thanor equal to about 70 weight percent preferred, and less than or equal toabout 60 weight percent more preferred. Also preferred within this rangeis an amount of poly(arylene ether) greater than or equal to about 20weight percent, with greater than or equal to about 30 weight percentmore preferred, and greater than or equal to about 40 weight percenteven more preferred. Within this range the amount of poly(alkenylaromatic) may be less than or equal to about 80 weight percent, lessthan or equal to about 70 weight percent preferred, and less than orequal to about 60 weight percent more preferred. Also preferred withinthis range is an amount of poly(alkenyl aromatic) greater than or equalto about 20 weight percent, greater than or equal to about 30 weightpercent preferred, and greater than or equal to about 40 weight percentmore preferred.

The polymeric composition may further comprise various impact modifiersfor improving the ductility of the composition. Useful impact modifiersinclude the elastomeric block copolymers, for example, A-B-A triblockcopolymers and A-B diblock copolymers as well as other multiblocks suchas A-B-A-B and B-A-B-A-B block copolymers. These various blockcopolymers are thermoplastic rubbers comprised of alkenyl aromaticblocks that are generally styrene blocks and rubber blocks, e.g., abutadiene block, which may be partially or totally hydrogenated.Examples of typical species of block copolymers includepolystyrene-polybutadiene (SBR), polystyrene-poly(ethylene-propylene)(SEP), polystyrene-polyisoprene,poly(alpha-methylstyrene)-polybutadiene,polystyrene-polybutadiene-polystyrene (SBS),polystyrene-poly(ethylene-butylene)-polystyrene (SEBS),polystyrene-polyisoprene-polystyrene andpoly(alpha-methylstyrene)-polybutadiene-poly(alpha-methylstyrene), aswell as the selectively hydrogenated versions thereof. In order toretain physical properties after long term elevated temperature aging orafter high processing temperatures, the partially or totallyhydrogenated block copolymers are often preferred. Block sizes can alsobe adjusted in order to maintain optical clarity when formed intovarious articles. Useful block copolymers are available commerciallyfrom a number of sources, including Phillips Petroleum Co., LTD. underthe trademark SOLPRENE, Kraton Polymers under the trademark KRATON,Dexco Polymers LP under the tradename VECTOR, Asahi Kasei ChemicalCorporation under the tradenames ASAFLEX and TUFTEC, and Kuraray Co.,LTD. under the trademark SEPTON.

Other useful impact modifiers include the so-called core-shell polymersbuilt up from a rubber-like core on which one or more shells have beengrafted. The core usually consists substantially of an acrylate rubber,butadiene rubber, or silicon-based rubber. One or more shells have beengrafted on the core. Usually these shells are built up for the greaterpart from a vinylaromatic compound and/or a vinylcyanide and/or analkyl(meth)acrylate and/or (meth)acrylic acid. In a preferredembodiment, the shell is mainly derived from vinylaromatic compound,preferably styrene and/or alpha-methylstyrene, in order to provide goodcompatibility between the impact modifier and the polymer composition.The core and/or the shell(s) often comprise multi-functional compoundsthat may act as a cross-linking agent and/or as a grafting agent. Thesepolymers are usually prepared in several stages using well-knownemulsion chemistry. The particle size and composition can be adjusted tomaintain optical clarity and enhanced ductility when formed into variousarticles. The core-shell polymers are available commercially from anumber of sources, including from Rohm and Haas Company under thetradename PARALOID.

Additional impact modifiers include the block and graft copolymers ofpoly(arylene ether) and polysiloxanes. Generally the block copolymersare more preferred and have A-B and A-B-A structures wherein the Ablocks represent the poly(arylene ether). The preparation of thesecopolymers is well-known in the art and typically involvesredistribution of an hydroxy terminated siloxane with a poly(aryleneether). The molecular weights of each component, hydroxy terminatedsiloxane with a poly(arylene ether), as well as their weight ratios canbe readily optimized based, at least in part, on the desired physicalproperties desired in the filtered polymeric composition.

The impact modifier may be present in the polymeric composition in anamount effective to increase the ductility of the composition and istypically used in an amount up to about 12.0 weight percent, or, morepreferably, in an amount of about 6.0 weight percent, wherein the weightpercents are based on the total weight of the polymeric composition.

Also contemplated are filtered polymeric materials further comprisingother resins in addition to the poly(arylene ether) and/or thepoly(alkylene aromatic). Examples of such other resins includepolyamides, poly(phenylene sulfide)s, polyetherimides, polyolefins, andthe like.

The filtered polymeric material may, optionally, further comprise anadditive selected from flame retardants, mold release agents and otherlubricants, antioxidants, thermal stabilizers, ultraviolet stabilizers,pigments, dyes, colorants, anti-static agents, conductive agents,fillers, and the like, and a combination comprising at least one of theforegoing additives. Selection of particular additives and their amountsmay be performed by those skilled in the art. If the additives arepresent in the polymeric material prior to filtration, the additiveshould be selected so as to not interfere with the particular filtrationsystem chosen for the method. Optionally, additives may be added to thefiltered polymeric material after the filtration step by methods knownin the art, either prior to or post isolation of the filtered polymericmaterial. Furthermore, for some applications the presence of theadditives must not adversely affect the surface quality or radial tiltproperties of articles molded from the material. Special processingconditions during molding may be required to ensure an adequately smoothsurface when molding filled articles.

Examples of pigments and dyes known to the art include those describedin the chapter “Colorants” in “Plastic Additives Handbook, 4^(th)Edition” R. Gachter and H. Muller (eds.), P. P. Klemchuck (assoc. ed.)Hansen Publishers, New York 1993.

Colorants include organic and inorganic pigments and dyes. Suitableinorganic colorants include carbon black, iron oxide, titanium dioxide,zinc oxide, zinc sulfide, and the like. Suitable organic colorantsinclude those from the following chemical classes: anthanthrone,anthraquinone, benzimidazolone, diketopyrrolo-pyrrole, dioxazine, diazo,indanthrone, isoindoline, isoindolinone, naphthol, perinone, perylene,phthalocyanine, pyranthrone, quinacridone, quinophthalone, and the like.

The filtered polymeric material may also comprise flame retardantsincluding non-halogenated flame retardants such as phosphate flameretardants, and halogenated flame retardants. Examples of suitable flameretardants include those found in the “Plastic Additives Handbook” underthe chapter “Flame Retardants”.

In one embodiment, prior to melt filtration, the poly(arylene ether)and/or poly(alkenyl aromatic) may be dissolved in a suitable solvent toform a solution which may be filtered through one or more solutionfiltration systems to form a filtrate. The poly(arylene ether) and/orpoly(alkenyl aromatic) may be isolated from the filtrate prior to itsintroduction to the extruder employed to form the melt. Optionally thefiltrate may be concentrated to a weight percent solids to form aconcentrate which is then fed to the extruder comprising the meltfiltration system. A weight percent solids of the concentrate comprisingpoly(arylene ether) and/or poly(alkenyl aromatic) may range from about10 to about 99 weight percent based on the total weight of polymericmaterial and solvent.

Suitable solvents for use in the solutions to be filtered from theabove-described embodiment include a halogenated aromatic solvent, ahalogenated aliphatic solvent, a non-halogenated aromatic solvent, anon-halogenated aliphatic solvent, or a mixture thereof. Suitablehalogenated aromatic solvents include, but are not limited to,halobenzenes, ortho-dichlorobenzene, chlorobenzene, and the like.Suitable halogenated aliphatic solvents include, but are not limited to,chloroform, methylene chloride, 1,2-dichloroethane, and the like.Suitable non-halogenated aromatic solvents include, but are not limitedto, benzene, toluene, xylenes, anisole, nitrobenzene, and the like.Suitable non-halogenated aliphatic solvents include, but are not limitedto, acetone, ethyl acetate, and the like. The solvent may be the same asthe polymerization solvent employed in the process of producing apoly(arylene ether) resin.

Suitable solution filtration systems include filters made from a varietyof materials such as, but not limited to, sintered-metal fibers, cloth,polymeric fiber, natural fiber, paper, metal mesh, pulp, ceramic, or acombination of the foregoing materials, and the like.

The geometry of the filter employed in the solution filtration systemmay be cone, pleated, candle, stack, flat, wraparound, or a combinationof the foregoing, and the like.

The pore size of the filter employed in the solution filtration systemmay be of any size ranging from 0.01 to 100 micrometer, or greater.Within this range, a pore size of less than or equal to about 50micrometers can be employed, with less than or equal to about 20micrometers preferred, and less than or equal to about 15 micrometersmore preferred. Also preferred within this range is a pore size ofgreater than or equal to about 0.1 micrometer, with greater than orequal to about 3 micrometers more preferred, and greater than or equalto about 5 micrometers especially preferred.

Suitable solution filtration processes may include gravity filtration,pressure filtration, vacuum filtration, batch filtration, continuousfiltration, or a combination of the foregoing filtration methods, andthe like.

There is no particular limitation on the method by which thepoly(arylene ether) and/or poly(alkenyl aromatic) may be isolated fromthe filtrate. Generally preferred are those isolation methods andassociated processes that do not re-introduce a significant number ofimpurities and black specks into the filtered material. Suitableprocesses known in the art to remove a solvent from a resin aregenerally applicable. Such processes include, but are not limited to,precipitation, distillation, spray drying, film evaporation,devolatilization, and the use of flash vessels to evaporate the solvent.The several processes described herein for isolation may be used aloneor in combination. When isolated, the poly(arylene ether) and/orpoly(alkenyl aromatic) may be in the form of a powder, pellet, flake ora feed directly from the isolation process to the extruder comprisingthe melt filtration system.

Many of the isolation processes described above may be used toconcentrate the filtrate without entirely removing the solvent from thefiltrate, but instead to provide a concentrate having an increasedpercent solids which may be fed into the extruder employed for meltfilter. When a concentrate is fed into the extruder, the extruder ispreferably a devolatilization extruder capable of removing solvent inthe melt.

Devolatilizing extruders and processes are known in the art andtypically involve a twin-screw extruder equipped with multiple ventingsections for solvent removal. The devolatilizing extruders most oftencontain screws with numerous types of elements adapted for suchoperations as simple feeding, devolatilization and liquid sealformation. These elements include forward-flighted screw elementsdesigned for simple transport, and reverse-flighted screw andcylindrical elements to provide intensive mixing and/or create a seal.Particularly useful are counterrotating, non-intermeshing twin screwextruders, in which one screw is usually longer than the other tofacilitate efficient flow through the die of the material beingextruded. Such equipment is available from various manufacturersincluding Welding Engineers, Inc.

In one embodiment, isolation comprises pre-concentration of the filtrate(partial evaporation of the solvent) and devolatilization extrusionsteps. During pre-concentration, the major part of the solvent isremoved by evaporation, preferably at an elevated temperature, forexample, in the range from about 150 to about 300° C., more preferablyin the range of about 180 to about 260° C., and/or elevated pressure,for example in the range from about 2 to about 75 bar, more preferablyin the range of about 5 to about 50 bar. Pre-concentration removes about1.0 to 99 percent of the solvent present in the filtrate. Within thisrange preferably less than or equal to about 90 percent, more preferablyless than or equal to about 80 percent of the solvent is removed.Pre-concentration is followed by devolatilization extrusion to removethe residual solvent.

If a pre-concentration step is used before the devolatilization step,the filtrate is preferably concentrated to about 10 to about 99 weightpercent solids level based on the total of solvent and polymericmaterial. Concentrated solutions of the filtrate may be isolated fromthe remaining solvent by a devolatilization process.

In another embodiment, a method of purifying a polymeric materialcomprises melt blending poly(arylene ether) and poly(alkenyl aromatic)in a twin screw extruder to form a melt; and melt filtering the meltthrough a melt filtration system to produce a filtered polymericmaterial; wherein the extruder has a specific throughput rate of about0.5 kg/cm³ to about 8 kg/cm³.

In one embodiment, a method of purifying a polymeric material comprisesmelt blending about 60 to about 30 weight percent of poly(phenyleneether) and about 40 to about 70 weight percent of polystyrene based onthe total weight of poly(phenylene ether) and polystyrene in an extruderto form a melt; and melt filtering the melt through a melt filtrationsystem to produce a filtered polymeric material, wherein the filteredpolymeric material is substantially free of visible particulateimpurities; and wherein the melt has an average residence time in theextruder of less than or equal to about 1 minute.

In yet another embodiment, articles are made from the filtered polymericmaterials prepared by any one of the methods presented herein.Particularly preferred articles include data storage media, such as butnot limited to, optical, magneto, or magneto-optical data storage media.Such media include compact discs, re-writable compact discs, digitalversatile disks, high density disks for data archival technology (DVR,such as BLU-RAY Disc), and the like.

In a preferred embodiment, the substrate layer for storage media aremade from the filtered polymeric materials prepared by any one of themethods presented herein. These storage media are preferably capable ofbeing read with a light source having a wave length of 405 nm andpreferably, having an objective-lens numerical aperture of 0.85.Alternatively, these storage media are preferably capable of being readwith a light source having a wave length of 450 nm and an objective-lensnumerical aperture of 0.65. Media having decreased wave lengths and ahigher objective-lens numerical aperture to increase the overallcapacity of the storage media are also contemplated; however, withpossible decreased optical tolerances.

The articles may be made by a variety of molding and processingtechniques. Suitable techniques to form articles include injectionmolding, foaming processes, injection-compression, rotary molding, twoshot molding, microcellular molding, film casting, extrusion, pressmolding, blow molding, direct molding (see generally WO 02/43943 toAdedeji et al.), and the like. A preferred technique is injectionmolding.

In one embodiment, the substrate layer is prepared by injection moldingthe filtered polymeric composition of poly(arylene ether) andpoly(alkenyl aromatic) to form a disk substrate having reduced molded instresses through the control of the injection molding parameters.Reduced molded in stresses in the substrate provides a disk assemblyhaving increased dimensional stability, thereby exhibiting minimal tiltwhen the assembly is exposed to elevated temperatures. When injectionmolding a filtered polymeric composition of poly(arylene ether) andpoly(alkenyl aromatic), a melt temperature of about 330 to about 370° C.may be used. Within this range a melt temperature of greater than orequal to about 340° C. is preferred, with greater than or equal to about350° C. more preferred. Also within this range a melt temperature ofless than or equal to about 360° C. is preferred, with less than orequal to about 355° C. more preferred.

Also within the previous embodiment, a mold temperature of about 90 toabout 130° C. may be used. Within this range a mold temperature ofgreater than or equal to about 100° C. may be used, with greater than orequal to about 110° C. preferred, and with greater than or equal toabout 115° C. more preferred. Also within this range a mold temperatureof less than or equal to about 125° C. is preferred, with less than orequal to about 120° C. more preferred. A clamp tonnage of greater thanor equal to about 12 tons may be used, preferably greater than on equalto about 20 preferred and greater than or equal to about 35 morepreferred.

When injection molding to prepare the substrate of the filteredpolymeric composition, a cool time of about 1 to about 35 seconds may beused. Within this range a cool time of greater than or equal to about 5seconds is preferred, with greater than or equal to about 7 seconds morepreferred, and greater than or equal to about 12 seconds even morepreferred. Also within this range a cool time of less than or equal toabout 25 seconds may be used, with less than or equal to about 20seconds preferred, and less than or equal to about 15 seconds morepreferred.

Futhermore, when injection molding to prepare the substrate from thefiltered polymeric composition, a hold pressure of about 1 to about 40kgf/cm² may be used. Within this range a hold pressure of greater thanor equal to about 5 kgf/cm² is preferred, with greater than or equal toabout 10 kgf/cm² more preferred, and greater than or equal to about 15kgf/cm² even more preferred. Also within this range a hold pressure ofless than or equal to about 35 kgf/cm² may be used, with less than orequal to about 30 kgf/cm² preferred, and less than or equal to about 25kgf/cm² more preferred.

If the filtered polymeric material is used to form a data storage mediasubstrate, for example, additional processing such as electroplating,coating techniques (spin coating, spray coating, vapor deposition,screen printing, painting, dipping, sputtering, vacuum deposition,electrodeposition, meniscus coating, and the like), lamination, datastamping, embossing, surface polishing, fixturing, and combinationscomprising at least one of the foregoing processes, among othersconventionally known in the art, may be employed to dispose desiredlayers on the polymeric material substrate. Essentially, the substratemay optionally be formed, in situ, with the desired surface featuresdisposed thereon on one or both sides, a data storage layer such as amagneto-optic material also on one or both sides, and an optionalprotective, dielectric, and/or reflective layers. The substrate can havea substantially homogenous, tapered, concave, or convex geometry, withvarious types and geometries of reinforcement optionally employed toincrease stiffness without adversely effecting surface integrity andsmoothness.

An example of a polymeric material storage media comprises an injectionmolded filtered polymeric material substrate that may optionallycomprise a hollow (bubbles, cavity, and the like) or filled (metal,plastics, glass, ceramic, etc., in various forms such as fibers,spheres, etc.) core. Disposed on the substrate are various layersincluding: a data layer, dielectric layer(s), a reflective layer, and/ora protective layer. These layers comprise conventional materials and aredisposed in accordance with the type of media produced. For example, fora first surface media, the layers may be protective layer, dielectriclayer, data storage layer, dielectric layer, and then the reflectivelayer disposed in contact with the substrate. A preferred data storagemedia that may be prepared from the polymeric material described hereinis disclosed in application Ser. No. 10/648609 entitled “SUBSTRATE ANDSTORAGE MEDIA FOR DATA PREPARED THEREFROM” filed Aug. 26, 2003 andcopending with the present application.

In one embodiment, the storage media comprises a substrate layer,preferably having a thickness of 1.1 mm, made from a filtered polymericcomposition prepared by any one of the methods presented herein. Thestorage media further contains data set adjacent to the substrate layerand a cover layer set adjacent to the data and opposite to substratelayer to assemble a structure of substrate layer—data—cover layer,although addition layers, e.g., reflective layer and adhesive layer, maybe placed in between the sequence of this structure. The cover layer hasa thickness of 100 micrometers or less through which a light sourcepasses to read, write, or read and write the data. The foregoing isoften referred to as a “single layer disc.” In another preferredembodiment, the substrate layer of a storage media is made from thefiltered polymeric materials prepared by any one of the methodspresented herein and preferably has a thickness of 1.1 mm and furthercontains a first recording layer set adjacent to the substrate layerfollowed by a spacer layer of 25 micrometers thickness, a secondrecording layer, and a cover layer having a thickness of 75 micrometersthrough which the light source passes to read, write, or read and writedata to the recording layers. The foregoing arrangement of layers isoften referred to as a “dual layer disc.” In all instances, it isimportant that the cover layer have a high accuracy for the desiredthickness, high transmittance of the laser light, e.g., 405 nm, and lowbirefringence. Additionally, for storage media that will not becontained within a protective case, the cover layer needs to providescratch resistance and finger print resistance. Consequently, in manyinstances the cover layer will contain multiple layers that incombination have the desired thickness. For example, a desired 100micrometer “cover layer” may contain a 98 micrometer actual cover layerwith a 2 micrometer hard coat layer to achieve the desired scratch- andfingerprint-resistances.

The actual layer compositions between the substrate layer made from thefiltered polymeric materials prepared by any one of the methodspresented herein, and the cover layer can vary widely depending on theformat-type of the storage media. For example, different layers areutilized for read-only media, write-once media, and rewritable media aswell as for single layer and dual layer media and various lightwavelengths and objective-lens numerical apertures. It is contemplatedthat the filtered polymeric materials prepared by any one of the methodspresented herein will have utility as the substrate layer of a storagemedia regardless of the ancillary layers utilized.

It should be clear that the present invention includes a poly(aryleneether)/poly(alkenyl aromatic) composition having, on average, less that1 particulate, preferably less that 0.5 particulate, and more preferablyno particulates, of 175 micrometer, preferably 140 micrometer, morepreferably 100 micrometer, average diameter per gram of the compositionand a method to prepare such composition. It should also be clear thatthe present invention includes a poly(arylene ether)/poly(alkenylaromatic) composition having on average less than 10 particulates,preferably less that 5 particulates, and more preferably less than 3particulates, of 50 micrometer average diameter per gram of thecomposition and a method to prepare such composition. It should be clearthat the present invention includes a poly(arylene ether)/poly(alkenylaromatic) composition having on average less than 10 particulates,preferably less than 5 particulates, preferably less than 3particulates, of 40 micrometer average diameter per gram of thecomposition and a method to prepare such composition. It should also beclear that the present invention includes a poly(aryleneether)/poly(alkenyl aromatic) composition having on average less than 30particulates, preferably less than 20 particulates, more preferably lessthan 10, and yet more preferably less than 5 particulates, of 30micrometer average diameter per gram of the composition and a method toprepare such composition. Further, it should be clear that the presentinvention includes a poly(arylene ether)/poly(alkenyl aromatic)composition having on average less than 200 particulates, preferablyless than 50 particulates, more preferably less than 40 particulates,and yet more preferably less than 25 particulates, of 20 micrometeraverage diameter per gram of the composition and a method to preparesuch composition. It should be clear that the present invention includesa poly(arylene ether)/poly(alkenyl aromatic) composition having lessthan 60 particulates, preferably less than 50 particulates, morepreferably less than 40 particulates, within the range of 20 to 100micrometer average diameter per fifteen gram of the composition and amethod to prepare such composition. The aforementioned particlediameters are based on an average of five measurements made on eachsample, i.e. five sample measurements.

The present invention also includes a data storage medium having asubstrate layer comprising a filtered polymeric composition containingpoly(arylene ether) resin and poly(alkenyl aromatic) resin as providedherein; wherein the substrate layer has less than fifty particulateshaving average particle diameters within the range of 20 to 100micrometers, more specifically within the range of 30 to 100micrometers. In a preferred embodiment, the aforementioned substrateadditionally contains no particulates having average particle diameterslarger than 175 micrometers, more specifically no particles havingaverage particle diameters larger than 100 micrometers.

In one embodiment, a method of purifying a polymeric composition,comprises melt blending poly(arylene ether) and poly(alkenyl aromatic)in an extruder to form a melt; and melt filtering the melt through amelt filtration system to produce a filtered polymeric composition;wherein the filtered polymeric composition has, based on an average offive sample measurements, at least one of: (a) less than 200particulates having an average diameter of 20 micrometers per gram ofthe filtered polymeric material, (b) less than 30 particulates having anaverage diameter of 30 micrometers per gram of the filtered polymericmaterial, (c) less than 5 particulates having an average diameter of 50micrometers per gram of the filtered polymeric material, (d) less than50 particulates within the range of 20 to 100 micrometers averagediameter per fifteen grams of the filtered polymeric material, and (e)zero particulates having an average diameter of at least 175 micrometersper gram of the filtered polymeric material. The method furthercomprises at least one of (a) pelletizing the filtered polymericcomposition, (b) filtering a solution comprising solvent andpoly(arylene ether) through a solution filtration system to form afiltrate, removing solvent from the filtrate to form a concentratecomprising the poly(arylene ether), (c) operating the extruder at aspecific throughput rate of about 0.5 kg/cm³ to about 8 kg/cm³, whereinthe extruder is a twin-screw extruder, (d) operating the melt filteringwherein the melt has an average residence time in the extruder of lessthan or equal to about 1 minute, (e) melt blending the melt with anadditive selected from the group consisting of flame retardants, moldrelease agents, lubricants, antioxidants, thermal stabilizers,ultraviolet stabilizers, pigments, dyes, colorants, anti-static agents,conductive agents, and combinations comprising at least one of theforegoing additives, (f) melt blending the melt with an impact modifier,(g) locating the melt filtration system at the die head of the extruder,(h) blanketing of the internal free space of the extruder with an inertgas, (i) using a melt pump, (j) melt filtering under conditions whereinless than a five-fold pressure drop is observed as compared to theinitial pressure drop obtained with a clean filtration system, (k) usingan in-line or off-line quality monitoring system, (l) cooling the meltwith de-ionized filtered water, (m) melt filtering the melt in a Class100 environment, (n) packaging the filtered polymeric composition in aClass 100 environment, (o) wherein the melt filtration system comprisesa by-pass system, and (p) pelletizing the filtered polymeric compositionwith an underwater die-face pelletizer system or a water ring pelletizersystem.

In one embodiment, a data storage medium comprises a substrate layer,data and a cover layer, wherein the data is located between thesubstrate layer and the cover layer, wherein the cover layer has athickness of 100 micrometers or less through which a light source passesto read, write, or read and write the data; wherein the substrate layercomprises a filtered polymeric composition; wherein the filteredpolymeric composition comprises about 90 to about 10 percent by weightof poly(arylene ether) resin and about 10 to about 90 percent by weightof poly(alkenyl aromatic) resin and wherein the filtered polymericcomposition has, based on an average of five sample measurements, atleast one of: (a) less than 200 particulates having an average diameterof 20 micrometers per gram of the filtered polymeric material, (b) lessthan 30 particulates having an average diameter of 30 micrometers pergram of the filtered polymeric material, (c) less than 5 particulateshaving an average diameter of 50 micrometers per gram of the filteredpolymeric material, (d) less than 50 particulates within the range of 20to 100 micrometers average diameter per fifteen grams of the filteredpolymeric material, and zero particulates having an average diameter ofat least 175 micrometers per gram of the filtered polymeric material.

All cited patents, patent applications, and other references areincorporated herein by reference in their entirety. The invention isfurther illustrated by the following non-limiting examples.

EXAMPLES

Four example runs (Example runs 1–4) were performed to illustrate themethod of melt filtering a melt comprising polyphenylene ether andpolystyrene to form a polymeric material having reduced levels ofparticulate impurities.

Example run 1: A 40/60 percent by weight blend of polyphenylene ether(PPE, powder, 0.33 IV available from GE Advanced Materials, Plastics)and polystyrene (xPS, Novacor 2272; Mw 214,000, Mn 71,600, Mw/Mn 2.99;available from Nova Chemical) was compounded in a 40 millimeter (mm)twin screw compounder equipped with a vacuum vent. A vacuum was appliedto the vent at about 20 inches of mercury (508 millimeters of Hg). Thecompounded material was fed to a single screw extruder equipped with 3barrels (zones). The extruder was equipped with a sintered metal fiberfilter (PALL, 3 micrometer pores, candle geometry) located at theextruder die head.

The extruded melt strands were run through a clean, filtered water bath,the water having been filtered through a 10 micrometer filter to removerust and impurities. The cooled strands of extruded polymeric materialwere dried and pelletized. Batches of the extruded melt were collectedthroughout the run, about every half hour. The extruder processingconditions are provided in Table 1.

The procedure of Example run 1 was repeated for Example run 2 exceptthat a 30 mm twin screw extruder was employed. The extruder processingconditions for Example run 2 are also provided in Table 1.

The procedure of Example run 1 was repeated for Example runs 3 and 4.The PPE-xPS formulation for Example runs 3 and 4 was a 50/50 percent byweight blend of 0.33 IV PPE and EB3300 grade xPS (Mw 276,000, Mn 51,500,Mw/Mn 5.36; available from Chevron Phillips Chemical). A 40 mmtwin-screw extruder was used for Example run 3, while a 30 mm twin-screwextruder was used for Example run 4. The processing conditions forExample runs 3 and 4 are provided in Table 1. For all of the Examplesthe drive, rate, pressure, and melt temperature are averaged for theentire run.

TABLE 1 Example 1 2 3 4 Zone 1 (° C.) 232 232 232 232 Zone 2 (° C.) 260260 260 260 Zone 3 (° C.) 277 277 277 277 Filter 1 (° C.) 277 277 277277 Filter 2 (° C.) 277 277 277 277 Die (° C.) 277 277 277 277 Screw(rpm) 85 100 85 85 Drive (amps) 8.0 7.4 10.0 11.0 Rate (kg/hr) 6.1 6.97.0 6.8 Filter In Press. (kg/cm²) 198 227 201 275 Filter Out Press.(kg/cm²) 26 14 25 27 Filter In Melt Temp. (° C.) 278 318 279 281 FilterOut Melt Temp. (° C.) 292 298 296 296 Visible Specks (avg.) 3.3 2 1.61.7 Filter Type/pore size PALL PALL PALL PALL (micrometer) candle,candle, candle, candle, 3 3 3 3

Samples from the runs of Examples 1–4 were tested for visualparticulates according to the following procedure. Samples of polymericmaterial for each run were taken about every half hour for each of theExample runs (1–4). Each sample was tested twice for visibleparticulates. Particles of 30 micrometer average diameter or greater arereadily observed without magnification. Two ounce sample bottles withpolyseal caps were subjected to a stream of filtered air to remove anyparticulates present. The bottles were rinsed with a small amount ofHPLC grade chloroform (CHCl₃) and fifty milliliters (ml) of HPLC gradeCHCl₃ was added to each sample bottle. Using a lightbox, the number ofvisible specks or particulates was recorded for each CHCl₃ blank. A10.00 gram amount of a sample was weighed out on a clean aluminum panand added to one of the bottles containing CHCl₃. This procedure wasrepeated for every sample. The samples were allowed to dissolve and thenviewed in the lightbox for the presence of visible specks. An averagenumber of specks were calculated for each run, four runs total (Examples1–4). The results of the visible particle analysis for Example runs 1–4are found in Table 1. Typical visible speck numbers for similarcompositions prepared without the use of the melt filter are in excessof 50 for a 10 gram sample. These data are quite unexpected as with therelatively large number of specks in the unfiltered material, it wasexpected that the small pore size filter as used in these examples wouldplug rapidly. Additionally, it was expected that gelled particles woulddistort and pass through the filter leading to a significantly higherparticulate number. For comparative purposes, a 500 mesh woven metalscreen filter having pore openings of 25 micrometers afforded filteredmaterial having in excess of 10 visible specks, i.e. specks greater than30 micrometers, per 10 gram sample. It should be clear that oneembodiment of the present invention is a method to make a compositioncomprising poly(arylene ether) and poly(alkyenyl aromatic) that has lessthat 20 visible specks, preferably less than 10 visible specks, morepreferably less than 5 visible specks, per 10 gram sample.

Several samples from the runs of Examples 1–4 were additionally analyzedto obtain a size distribution of the particulate contaminants present inthe materials. Two samples from Example run 2 (Ex. 2, S1 and Ex. 2, S2),one sample from Example run 3 (Ex. 3, S1), and two samples from Examplerun 4 (Ex. 4, S1 and Ex. 4, S2) were tested for particulate contentaccording to the procedure below. Amounts of particulates having sizesranging from 5 micrometers to 100 micrometers were determined using aPacific Instruments ABS2 analyzer that employs a laser light scatteringtechnique. A 40.0 gram amount of each sample was dissolved in 400 ml ofHPLC grade CHCl₃ contained in a clean polyethylene bottle. A 20 mlquantity of each sample solution was allowed to flow through the ABS2analyzer detector at a flow rate of 1 ml/minute (±5%). The amount ofparticulates of varying sizes present in the sample was measured in thedetector during this process. Each sample was tested five times andaveraged to yield a final number. Two comparative examples were preparedand tested. Comparative Example 1 (CE 1) was an unfiltered blend of50/50 weight percent 0.33 IV PPE/EB3300 grade xPS. Comparative Example 2(CE 2) was optical quality polycarbonate (OQ-PC, LEXANO®1050 availablefrom GE Advanced Materials, Plastics). The results of the ABS2 analyzerparticle analysis in particles per gram can be found in Table 2, alongwith the blank data (CHCl₃ alone).

TABLE 2 Particulate Size (micrometers) 5 10 15 20 30 40 50 100 Example,Sample # Particles per gram Ex. 2, S1 654.3 111 38.7 23.3 3.2 0.9 1.20.1 Ex. 2, S2 561.8 91.1 34.4 16.5 1.9 0.4 0.6 0.1 Ex. 3, S1 689.8 9032.7 15.6 2.6 0.5 0.4 0.1 Ex. 4, S1 1919.9 143.7 44.3 20.1 2.4 0.6 0.2 0Ex. 4, S2 1117.5 114.8 42.9 26.6 3.6 1.8 0.2 0 CE 1 6901.25 1237.5 500396.25 85 23.75 30 5 CE 2 317.000 58.88 52.88 14.88 3.38 0.75 0 0 CHCl₃15.15 3.65 1.25 0.25 0 0 0 0

The results of the above experiments show a significant reduction in theoverall number particulate impurities between the unfiltered sample(CE 1) and the filtered samples (Ex. 2, S1; Ex. 2, S2; Ex. 3, S1; Ex. 4,S1; and Ex. 4, S2). Furthermore, the particulate impurity level of theExamples of the present method is comparable to or better than OQ-PC (CE2) with regard to particulates of 15 micrometers or greater. It is quiteunexpected that such a large reduction in the number of particles pergram in a poly(arylene ether)/poly(alkenyl aromatic) composition wasobtained over the particle size range between 20 and 100 micrometersthrough the use of a sintered metal fiber filter. As previouslyexplained, it was expected that the poly(arylene ether)/poly(alkenylaromatic) composition would foul or plug the filter rapidly and eitherpush larger particles through the filter or collapse the filter. Incontrast, the procedure of Example run 1 using a 40 mm twin screwextruder was repeated with a run time using the same melt filtrationsystem in excess of 40 continuous hours with less than a 10% increase inthe back pressure as measured at a location immediately before the meltfiltration system and unexpectedly, without a significant increase inthe number of particulates observed in the filtered polymericcomposition even after 40 hours of continuous operation. It wasadditionally expected that the poly(arylene ether)/poly(alkenylaromatic) composition would have to be run only at a very low specificthroughput rate. However, in contrast, specific throughput rates inexcess of 5 kg/hr/cm³ were unexpectedly achieved.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing fromessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A filtered polymeric composition, wherein the filtered polymericcomposition comprises about 90 to about 10 percent by weight ofpoly(arylene ether) resin and about 10 to about 90 percent by weight ofpoly(alkenyl aromatic) resin, and wherein the filtered polymericcomposition has, based on an average of five sample measurements, atleast one of: (a) less than 200 particulates having an average diameterof 20 micrometers per gram of the filtered polymeric material, (b) lessthan 30 particulates having an average diameter of 30 micrometers pergram of the filtered polymeric material, (c) less than 5 particulateshaving an average diameter of 50 micrometers per gram of the filteredpolymeric material, (d) less than 50 particulates having an averagediameter within the range of 20 to 100 micrometers per fifteen grams ofthe filtered polymeric material, and (e) zero particulates having anaverage diameter of at least 175 micrometers per gram of the filteredpolymeric material.
 2. The filtered polymeric composition of claim 1,wherein the poly(arylene ether) comprises at least one of (a)poly(2,6-dimethyl-1,4-phenylene ether) and (b)poly(2,6-dimethylphenylene ether-co-2,3,6-trimethylphenylene ether), andwherein the poly(arylene ether) has an intrinsic viscosity of about 0.10to about 0.60 deciliters per gram as measured in chloroform at 25° C.;and wherein the poly(alkenyl aromatic) is at least one of (i) atactichomopolystyrene and (ii) non-elastomeric block copolymer of styrene andone or more polyolefins.
 3. A method of purifying a polymericcomposition, comprising: melt blending poly(arylene ether) andpoly(alkenyl aromatic) in an extruder to form a melt; and melt filteringthe melt through a melt filtration system to produce a filteredpolymeric composition; wherein the filtered polymeric composition has,based on an average of five sample measurements, at least one of: (a)less than 200 particulates having an average diameter of 20 micrometersper gram of the filtered polymeric material, (b) less than 30particulates having an average diameter of 30 micrometers per gram ofthe filtered polymeric material, (c) less than 5 particulates having anaverage diameter of 50 micrometers per gram of the filtered polymericmaterial, (d) less than 50 particulates having an average diameterwithin the range of 20 to 100 micrometers per fifteen grams of thefiltered polymeric material, and (e) zero particulates having an averagediameter of at least 175 micrometers per gram of the filtered polymericmaterial.
 4. The method of claim 3, wherein the melt filtration systemcomprises a sintered-metal filter, a metal mesh filter, a fiber metalfelt filter, a ceramic filter, or a combination comprising at least oneof the foregoing filters.
 5. The method of claim 3, wherein the meltfiltration system comprises a filter having a geometry that is cone,pleated, candle, stack, flat, wraparound, or a combination comprising atleast one of the foregoing geometries.
 6. The method of claim 3, whereinthe melt filtration system comprises a filter having a pore size ofabout 1.0 to about 50 micrometers.
 7. The method of claim 3, furthercomprising at least one of: (a) pelletizing the filtered polymericcomposition, (b) filtering a solution comprising solvent andpoly(arylene ether) through a solution filtration system to form afiltrate, removing solvent from the filtrate to form a concentratecomprising the poly(arylene ether), (c) operating the extruder at aspecific throughput rate of about 0.5 kg/cm³ to about 8 kg/cm³, whereinthe extruder is a twin-screw extruder, (d) operating the melt filteringwherein the melt has an average residence time in the extruder of lessthan or equal to about 1 minute, (e) melt blending the melt with anadditive selected from the group consisting of flame retardants, moldrelease agents, lubricants, antioxidants, thermal stabilizers,ultraviolet stabilizers, pigments, dyes, colorants, anti-static agents,conductive agents, and combinations comprising at least one of theforegoing additives, (f) melt blending the melt with an impact modifier,(g) locating the melt filtration system at the die head of the extruder,(h) blanketing of the internal free space of the extruder with an inertgas, (i) using a melt pump, (j) melt filtering under conditions whereinless than a five-fold pressure drop is observed as compared to theinitial pressure drop obtained with a clean filtration system, (k) usingan in-line or off-line quality monitoring system, (l) cooling the meltwith de-ionized filtered water, (m) melt filtering the melt in a Class100 environment, (n) packaging the filtered polymeric composition in aClass 100 environment, (o) wherein the melt filtration system comprisesa by-pass system, and (p) pelletizing the filtered polymeric compositionwith an underwater die-face pelletizer system or a water ring pelletizersystem.
 8. The method of claim 3, wherein the poly(arylene ether)comprises at least one of (a) poly(2,6-dimethyl-1,4-phenylene ether) and(b) poly(2,6-dimethylphenylene ether-co-2,3,6-trimethylphenylene ether),and wherein the poly(arylene ether) has an intrinsic viscosity of about0.10 to about 0.60 deciliters per gram as measured in chloroform at 25°C.
 9. The method of claim 3, wherein the poly(alkenyl aromatic) is atleast one of (i) atactic homopolystyrene and (ii) non-elastomeric blockcopolymer of styrene and one or more polyolefins.
 10. A method ofpurifying a polymeric material, comprising: melt blending about 60 toabout 30 weight percent of poly(arylene ether) and about 40 to about 70weight percent of polystyrene based on the total weight of poly(aryleneether) and polystyrene in an extruder to form a melt; and melt filteringthe melt through a melt filtration system to produce a filteredpolymeric material, wherein the filtered polymeric material issubstantially free of visible particulate impurities, wherein the melthas a residence time in the extruder of less than or equal to about 1minute, and wherein the poly(arylene ether) comprises at least one of(a) poly(2,6-dimethyl-1,4-phenylene ether) and (b)poly(2,6-dimethylphenylene ether-co-2,3,6-trimethylphenylene ether). 11.An article comprising the filtered polymeric material of claim 1,wherein the article is formed by injection molding, blow molding,extrusion, sheet extrusion, film extrusion, profile extrusion,pultrusion, compression molding, thermoforming, pressure forming,hydroforming, or vacuum forming.
 12. A data storage medium comprisingthe filtered polymeric material prepared by the method of claim
 3. 13. Adata storage medium comprising a substrate layer, data and a coverlayer, wherein the data is located between the substrate layer and thecover layer, wherein the cover layer has a thickness of 100 micrometersor less through which a light source passes to read, write, or read andwrite the data; wherein the substrate layer comprises a filteredpolymeric composition comprising about 90 to about 10 percent by weightof poly(arylene ether) resin and about 10 to about 90 percent by weightof poly(alkenyl aromatic) resin; and less than fifty particulates havingaverage particle diameters within the range of 30 to 100 micrometers.14. The data storage medium of claim 13, wherein the substrate layercontains no particulates having average particle diameters larger than175 micrometers.
 15. A data storage medium comprising a substrate layer,data and a cover layer, wherein the data is located between thesubstrate layer and the cover layer, wherein the cover layer has athickness of 100 micrometers or less through which a light source passesto read, write, or read and write the data; wherein the substrate layercomprises a filtered polymeric composition; wherein the filteredpolymeric composition comprises about 90 to about 10 percent by weightof poly(arylene ether) resin and about 10 to about 90 percent by weightof poly(alkenyl aromatic) resin and wherein the filtered polymericcomposition has, based on an average of five sample measurements, atleast one of: (a) less than 200 particulates having an average diameterof 20 micrometers per gram of the filtered polymeric material, (b) lessthan 30 particulates having an average diameter of 30 micrometers pergram of the filtered polymeric material, (c) less than 5 particulateshaving an average diameter of 50 micrometers per gram of the filteredpolymeric material, (d) less than 50 particulates having an averagediameter within the range of 20 to 100 micrometers per fifteen grams ofthe filtered polymeric material, and (e) zero particulates having anaverage diameter of at least 175 micrometers per gram of the filteredpolymeric material.
 16. The filtered polymeric composition of claim 1,wherein the poly(alkenyl aromatic) is a non-elastomeric block copolymerderived from an alkenyl aromatic monomer having the structure (III) andon or more polyolefins, wherein structure (III) is

wherein R¹ is hydrogen, C₁–C₈ alkyl, or halogen; Z¹ is C₁–C₈ alkyl; andp is 0 to
 5. 17. The filtered polymeric composition of claim 16, whereinR¹ is hydrogen and Z¹ is C₁ alkyl.
 18. The method of claim 3, whereinthe poly(alkenyl aromatic) is a non-elastomeric block copolymer derivedfrom an alkenyl aromatic monomer having the structure (III) and one ormore polyolefins, wherein structure (III) is

wherein R¹ is hydrogen, C₁–C₈ alkyl, or halogen; Z¹ is C₁–C₈ alkyl; andp is 0 to
 5. 19. The method of claim 18, wherein R¹ is hydrogen and Z¹is C₁ alkyl.
 20. The data storage medium of claim 15, wherein thepoly(alkenyl aromatic) is a non-elastomeric block copolymer derived froman alkenyl aromatic monomer having the structure (III) and one or morepolyolefins, wherein structure (III) is

wherein R¹ is hydrogen, C₁–C₈ alkyl, or halogen; Z is C₁–C₈ alkyl; and pis 0 to
 5. 21. The data storage medium of claim 20, wherein R¹ ishydrogen and Z¹ is C₁ alkyl.
 22. The data storage medium of claim 12,wherein the data storage medium comprises a substrate layer, data and acover layer.
 23. The data storage medium of claim 22, wherein the coverlayer comprises a hard coat layer.